High-temperature thermometer



1 615 505 1927' G. w. w. CORNMAN ET AL HIGH TEMPERATURE THERMOMETEB Filed June 21 1 2 George-W. W.

and

Patented Jan. 25, 1927.

UNITED STATES PATENT OFFICE.

enown w.

VANIA, PENNSYLVANIA,

W. CORNMAN AND RICHARD P. BROWN, OF PHILADELPHIA, PENNSYL- ASSIGNORS TO THE BROWN INSTRUMENT COMPANY, OF PHILADELPHIA,

A CORPORATION OF. PENNSYLVANIA.

A HIGH-TEMPERATURE :rnnmvromnrnn.

Application filed .Tune 2,

inc present invention relates to temperature responsive devlces and indicators, such as thermometers,

and more particularly to devices of the vapor-actuated type, in which a body of liquid, suitably confined, is

posed to the temperature to be measured, and the pressure developed as a result of such "vaporization as occurs, means of a Bourdon tube, I

scale.

proved very valuable as is utilized, as by to actuate a pointer or other index associated with a suitable Such vapor actuated instruments have distance thermometers in cases where it is, desired to read 1 the temperature at some liquid containing vessel the temperature in question, because distance from the or bulb exposed. to

the

pressure developed in the bulb can readily be transmitted 2 very fine tube,

considerable distances 1n a such as a capillary tube con- 2 sive device may be exposed produce no sensible change in the vapor pressure of the liquid therein, and hence curac tage 1n compared to gas filled the latter operate by manent gas which, in

necting tube,

do not affect the acof the instrument. This is an advanfavor of the vapor-actuated type as thermometers, because the pressure of a perthe Bourdon and conis affected in the same way and in the same proportions as that in the bulb for'a given variation in temperature.

If, therefore, the Bourdon and the'connecting tube of a gas actuated instrument happen to be exposed to considerable temperature variation, 40

temperature of the gas in the bulb.

the reading of the instrument may not always correspond accurately to the Heretofore vapor-actuated thermometers have been subject to .the limitation that they could not be made to function satisfactorily except under relatively moderate tempera-,

tures, not exceeding some4=00 F., so that when higher temperatures mined only gas or mercury were available.

tion is to overcome the vapor-actuated instruments them fully available and satisfactory were to be deterfilledv instruments One of the objects of the present inventhis vital limitation of and to make for , ranging 1922. Serial No. 565,296

space per degree as the temperature in creases, andis usually graduated with two degree d1v1s1ons,--though the divisions are dependent, of course, upon the total scale range. hese and other advantages are made possible by the di scovery', through the present invention, that certain substances or materials characterized by a high critical temperature and by a boiling point not exceeding moderate limits, preferably toluol, will. be found satisfactory and accurate va porous actuating media for temperatures ranging from the boiling point of such mediu1n,,or a little lower, up to and above the critical temperature. With such substances, one and the same vapor-actuated instrument can be made to cover efficiently temperatures to 800 F., and upward.

Inthe foregoing, toluol has been referred to as the preferred substance or actuating medium because we have discovered that by ts use entirely new and distinctive results are obtainable in high temperature thermometer work, and particularly in the distant type of instrument. The boiling point of toluol, as is well known, is 230.5" F.

Its critical temperature 1s higher by about hitherto used or instruments of this characinto gaseous state.

ter, such as alcohol, ether, water, or sulphur dioxide. since instruments using such media are inherently subject to the limitations above set forth. An instrument constructed in accordance with the present invention operates like a vapor actuated i1 strument up to the critical temperature of its actuating medium, while at higher temperatures the instrument functions like a gas actuated instrument since at the critical temperature all of the medium is vaporized and passes The use of toluol as an actuating medium is especially advantageous r resenting the 450 because of its relatively low boiling point and its relatively high critical temperature, the latter being about 608 F. Toluol is especially advantageous, also, because its transition from the saturated vapor state to the unsaturated gaseous state at the critical temperature is not marked by .any abruptness, eccentricities, or irregularities that might make the scale graduation of the instrument in which it is used diflicult cramcertain in the critical of the scale range.

Among the special advantages of an instrument in which the scale range extends substantially to each side of the critical temperature of the actuating medium, is the great foreshortening of the scale indications of the instrument for the lower temperatures. For instance, when toluol is the medium in such an instrument as is shown in the annexed drawing, the chart distance rep- F. interval or temperature range from 50 F. to 500 F. is less than half that representing the'200 F. in-

terval or range from 500 F. to 700 F. This facilitates the proper reading of the scale indications for the higher temperatures as is ordinarily desirable in'an instrument intended for measuring temperatures var ing over a wide range. For temperatures a ove the critical temperature equal temperature differences are represented by substantially identical scale increments or distances.

The use of an actuating medium which, like toluol, has a relatively high critical temperature in aecordancewith the present invention to measure temperatures above and below said critical temperature, possesses the advantage over an instrument containing a gaseous medium for measuring temperatures over the same range that the errors due to temperature changes in pertions of the apparatus remote from the bulb exposed tothe temperature to be measured are minimized. This follows from 'the fact that the percentage errors, due to the ordinary atmospheric temperature variations to which the external parts of the measuring apparatus are subjected, decrease as the temperature measured increases. An instrument constructed in accordance with the present invention for measuring temperatemperature portion tures above and below the critical tempera ture of the actuating medium is thus inherently and intrinsically more accurate than an instrument in which the actuating medium is in the gaseous state throughout the same temperature range.

In the accompanying drawings, the figure represents a vapor-actuated recording thermometer embodying one form of the present invention, and showing a portion broken away for clearness of illustration.

Referring to the drawings one form of the present invention comprises an indicating instrument 10, here shown as of the long distance temperature recording type, having the usual pen arm or index 11, which is arranged to be actuated by a helical Bourdon tube 12, the unsealed end of which is connected to a bulb 13 by a flexible protectively armored tube 14, the bore of which is preferably of capillary fineness. This bulb 13 is arranged to be located in the heat zone the temperature of which is to be measured or indicated, and in the present instance is partially filled with a liquid 15, as toluol, which has such properties as above set forth. When the bulb 13. is inserted in the zone of heat whose temperature is to be measured, the pressure developed tends to uncurl the Bourdon 12 and thus causes the index 11 to move over the chart 16, which may be graduated and calibrated according to the principles above indicated, i. e., unevenly for temperatures below the critical point of the actuating medium, and evenly for higher 100 temperatures.

While but a single form is shown in which this invention may be embodied, it' is to be understood that the invention is not limited to any specific construction, but might be ap- 105 plied in various forms without departing from the spirit of the invention or the scope -of the appended claims.

Having thus described our invention, we claim 1. An expansion thermometer having pressure responsive indicating means for the measurement of temperatures over a predetermined range, and comprisin a fluid actuating medium having a critical temperature 115 intermediate the limits. of such range.

2. An expansion thermometer having pressure responsive means for the measurement of temperatures over a predetermined range, and comprising a fluid actuating medium 120 having a critical temperature much above ordinary atmospheric temperatures and adapted for measuring temperatures over a range extending above and below said critical temperature.

3. An expansion thermometer having pressure responsive indicating means for the measurement of temperatures over a predetermined range, and comprising toluol as its fluid actuating medium and adapted for measuring temperatures over a range extendsure variations resulting from, exposure of ing above the. critical temperature of toluol. the bulb to a temperature range extending 4. An expansion thermometer comprising above and below the critical temperature of in combination an indicating instrument insaid medium.

5 eluding an index and a Bourdon tube for Signed at Philadelphia; in the county of 15 actuating said index, a bulb, a conduit eon- Philadelphia, and State of Pennsylvania, necting said bulb and tube, and a fluid aetuthis 29 day of May, 1922. ating medium in said bulb, said bulb being i adapted to \vithstand, and said instrument GEORGE W. W. CQRNMAN.

I being adapted to indicate the internal pres- 1 RICHARD P. BROWN. 

